Defect Inspection Using Polarization Analysis
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Solution Overview
Problem
Conventional defect inspection methods for semiconductor wafers and other substrates face challenges in detecting defects like foreign particles and brightness variations due to film thickness differences, leading to false judgments and reduced sensitivity, especially when dealing with varying defect types and appearances.
Innovation Solution
A defect inspection apparatus that compares images of identical patterns using a system with a polarization detecting means to detect plural polarization components independently, extracting defect-indicative signals based on the distribution of vectors in a defined polarization component space, and employing feature quantities of pixels to identify excessively deviated values as defects, while utilizing a CPU configuration with parent and child CPUs for high-speed processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional image comparison methods are used to detect defects, then defect detection can be performed, but brightness differences caused by film thickness variations lead to false judgments and reduced sensitivity
Solution Approach 1:
The patent changes the detection parameter from luminance intensity to polarization state. By measuring the polarization characteristics of light reflected from or transmitted through the inspection subject, the system can distinguish between defects and brightness variations caused by film thickness changes, as these factors affect polarization differently than they affect luminance
Solution Approach 2:
The patent introduces polarization state as an intermediary parameter between the inspection subject and the detection system. By analyzing how light polarization changes when interacting with the sample, the system creates a reliable intermediate measurement that separates defect signals from noise caused by film thickness variations
2Adaptability or versatility
If multiple detection optical systems are used to detect various defects, then detection versatility improves, but system complexity increases
Solution Approach 1:
The patent makes a single detection optical system universal by enabling it to detect multiple types of defects through polarization analysis. The same optical system can identify foreign particles, film thickness variations, and pattern defects by analyzing different polarization state characteristics, eliminating the need for multiple specialized detection systems
3Productivity
If high-speed parallel processing is implemented, then processing speed improves, but coordination complexity between multiple CPUs increases
Solution Approach 1:
The patent segments the image processing tasks across multiple CPUs, with each CPU responsible for processing specific regions or aspects of the inspection data. This segmentation enables parallel processing while maintaining clear division of labor, reducing coordination complexity compared to fully distributed systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances defect detection sensitivity and accuracy by reducing brightness unevenness and noise, allowing for the detection of a wider variety of defects with high sensitivity and speed, even in cases where brightness differences occur due to film thickness variations, and accommodates varying defect types without compromising processing speed.
Implementation Method 1
a polarization detecting means for detecting plural different polarization components independently and producing plural signals corresponding to the respective polarization components
Data Source
AI summary
A pattern inspection apparatus which compares images of regions, corresponding to each other, of patterns that are formed so as to be identical and judges that non-coincident portions in the images are defects. The pattern inspection apparatus is equipped with an image comparing section which plots individual pixels of an inspection subject image in a feature space and detects excessively deviated points in the feature space as defects. Defects can be detected correctly even when the same patterns in images have a brightness difference due to a difference in the thickness of a film formed on a wafer.